my $sth = $dbh->prepare_cached(<<"+++end_of_sql_statement");
  SELECT emp_id, CONCAT(emp_last, ', ', emp_first), dept_name
  FROM sys_main.humans, sys_main.depts 
  WHERE status='AV' 
    AND dept_id=dept
  ORDER BY ?
+++end_of_sql_statement

$sth->execute($sort);